Study finds less-toxic brown widow variety may be taking over.

By Mary Elizabeth Dallas, HealthDay News

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THURSDAY, July 5, 2012 (HealthDay News) —What's bad news for the black widow spider may be good news for California homeowners: The less-toxic brown variety appears to be taking over.

Although they are relatively new to North America, a new study found that brown widow spiders may be displacing the black widow spiders that are native to southern California.

Researchers found the brown widow spider likes to hide outside people's homes. They noted, however, that it's less toxic than the black widow.

In conducting the study, the researchers performed time searches in various habitats, such as developed parks, urban properties and undeveloped natural areas to compare the abundance and habitat selection of the brown widow spider to that of the black widow spider.

Using data collected from 72 sites, the researchers found 20 times as many brown widows as black widows outside homes, especially under outdoor furniture and in tiny cracks in walls, fences and other objects. The researchers noted that none of the spiders was found inside people's homes.

"Homeowners would benefit to know about the hiding places of brown widows, displaying care when placing their hands in nooks and crannies," the study's authors wrote.

Brown widow spiders were first seen in Florida back in 1935, but they were not documented in southern California until 2003, the researchers pointed out.

"The brown widows really burst on to the scene in a very short time, and we found brown widows in many habitats where we expected to find black widows," study corresponding author Richard Vetter, of the University of California, Riverside, said in a Entomological Society of America news release. "There may be some competition where brown widows are displacing black widows because there is some habitat overlap. There are also places where only brown widows were able to make homes, but in other habitats the black widows still predominate."

The research was published in the July issue of theJournal of Medical Entomology.